Such a device is known from U.S. Pat. No. 4,059,240. It has a hollow axle, on which the storage drum of the intermittent storage is stationarily supported and the thread drum of the positive storage is rotatably supported. The thread which comes from a thread storage is fed to the storage drum by means of a winding-up member which rotates about said storage drum, and the thread is then pulled off overhead through the hollow axle. During its exit from the hollow axle the thread is guided through suitable guide members, is wound onto the thread drum of the positive storage and is pulled off from same tangentially. The two drums are thereby associated with one another such that the storage drum faces with its thread-supply area the thread drum, and same with its thread-removal area faces the storage drum, which results in a favorably short thread path from the storage drum to the hollow axle and from the hollow axle to the thread drum. The winding directions on both drums are the same; there exists the possibility to drive the winding-up device for the storage drum and the thread drum with one common drive, or upon exceeding a predetermined minimum storage size on the storage drum to uncouple same and to drive the positive storage alone. The known device is constructed compactly and space-savingly. However, the thread experiences on its way from the storage drum toward the thread drum several reroutings, for which suitable shapes of the drums or special guide members are needed.
The purpose of the invention is to construct a device of the abovedescribed type so that between both drums there is possible a thread transfer which is as short and direct as possible, and the thread is rerouted little.
In the inventive thread-storage and delivery device, the thread runs from the withdrawal or removal area of the storage drum on the shortest path to the thread drum. It experiences thereby one single rerouting, namely by the support member. The goal which is desired by the storages which are connected one behind the other is therewith achieved in a particularly high degree, namely to hold the thread tension at the positive storage as low and constant as possible.
During the thread transfer from the storage drum to the thread drum, only so much thread can be wound up onto the thread drum as is being unwound from the storage drum. Assuming the same drum diameters, this means theoretically that one winding is unwound from the storage drum. This, however, assumes that a nonelastic, nonexpandable thread is being used. An expandable thread is expanded depending on its elasticity during removal from the storage spool and during winding up onto the storage drum under tension. During an approximately tensionless transfer from the storage drum to the thread drum the expansion stops, the thread is shortened more or less depending on its elasticity. A winding on the thread drum receives therewith more threads than a winding on the storage drum. In order to achieve an even delivery, the relative peripheral speeds of both drums can be designed such with respect to one another, that the unwinding speed of the thread which comes from the storage drum is higher for a compensating speed which compensates for length changes of elastic threads during the transfer to the thread drum than the winding-up speed of the thread drum. It is assured therewith, that the thread storage on the positively delivering thread drum has substantially always the same size.
The thread transfer from the storage drum to the thread drum can occur in a simple manner through the support member by the storage drum being connected to a drive mechanism which controls its average peripheral speed: peripheral speed of the thread drum plus compensating speed. Such a drive control is for example possible with semiconductors, which operate dependent from a monitoring device of the thread storage on the storage drum. The speed of the storage drum, which is higher for the compensating speed, thus makes it possible, that the ideal transfer point between both drums, which lies on the support member, remains as much as possible stationarily with respect to the surroundings. If the speed differences between the drum rotations are temporarily greater than this, as made necessary by the thread elasticity, the transition point can wander. It moves thereby corresponding with the running direction of the thread, which belongs to the drum, which is quicker relative to its speed corresponding with the actual thread run.
As a support member it is possible to arrange advantageously a brake ring with elastic fingers on the storage drum. It assures even tension during removal of the thread from the storage drum and permits in a simple manner that the ideal transition point between both drums, which simultaneously represents the withdrawal point of the compensating storage and the feed point of the positive storage, can wander relatively to its surrondings.
An even thread delivery and an adjusting of the thread storages to both drums is assured in a simple manner by the storage drum of the compensating storage having associated with it a feed member which moves with respect to the storage drum, and the thread drum of the positive storage having associated with it a withdrawal member which is movable synchronously with the feed member. This means in each case at a rotating drum a stationary member, at a stopped drum a synchronously rotating member, for example a socalled flyer. Also possible is a flyer which rotates around a rotating drum in the same direction of rotation at twice the speed, or in the opposite direction at normal speed, when the drum rotates twice as fast. It is thereby true for the storage drum and a winding-up member, that the speed of the winding-up member must correspond with the speed of the thread which unwinds from the thread drum; the storage drum, however, in the transfer area gives its unwinding thread the necessary compensating speed.
In a different embodiment, the storage drum rotates only with a compensating speed; here a rotating winding-up member is associated, and the thread drum rotates in the same direction of rotation as the winding-up member and with approximately twice the speed and has a withdrawal member which rotates at the speed of the winding-up member. The relative speed between the withdrawal area of the storage drum and the winding-up area of the thread drum corresponds in this manner again approximately with the thread-delivery speed, which occurs in the case of the embodiment with two oppositely rotating drums in the transition area. In this device the transfer point wanders relative to its surroundings, namely in the direction which corresponds with the direction of rotation of the thread drum, at approximately half the peripheral speed of the thread drum. The thread drum winds in this manner during two rotations one winding on itself, thus as much as the withdrawal member which rotates at half the speed removes. From the storage drum is unwound during the same time so much more than one winding, as is necessary for balancing out the thread elasticity.
Furthermore in one embodiment it is possible to drive the storage drum for rotation and the storage drum can have a winding-up member which rotates in the same direction of rotation at half the speed of rotation, and the thread drum of the positive storage can stand still and can have a withdrawal member which rotates in the same direction and equally fast as the winding-up member. The withdrawal point wanders also in this device, namely in direction of rotation of the storage drum at approximately half the peripheral speed. The necessary compensating speed for the thread in the transfer area results from the control of the storage drum in dependency of its thread storage size.